Hi Eric,
> > ------------------------------------------------------------------
> > m4_syscmd([cat 1>&2 <<\EOT
> >
> > Here comes the definition of AM_INIT_AUTOMAKE:]
> > m4_defn([AM_INIT_AUTOMAKE])
> > [EOT])
> > ------------------------------------------------------------------
>
> Very similar to m4_file_append, except that it outputs to stderr rather
> than appending to a file. For that matter, m4_errprint does that, without
> having to spawn a subprocess.
Glad to see that m4_file_append and m4_errprintn already exist. I did not
know about them.
> Hmm, --trace shows arguments, not definition, but it also has a place.
Yes, I agree documenting --trace by example is good as well.
> +$ @kbd{cat <<\EOF > foo.m4}
> +m4_init
> +m4_errprintn([try one: m4_dquote is ]m4_defn([m4_dquote]))
> +m4_divert([0])dnl
> +m4_errprintn([try two: m4_dquote is ]m4_defn([m4_dquote]))dnl
> +m4_dquote([hi])
> +EOF
> +$ @kbd{autom4te --language=m4sugar foo.m4}
> +try one: m4_dquote is [$@@]
> +try two: m4_dquote is [$@@]
> +$ @kbd{cat foo}
> +[hi]
In this second example, the file 'foo' is never being created, since autom4te
is not being passed the options "-o foo".
More importantly, your example shows m4_errprintn only in the context of
"autom4te --language=m4sugar". But it's more powerful than that: it also
works from inside an 'autoconf' run (with is more often what the user wants
to debug).
Here is a proposed patch to
- show m4_errprintn in the context of autoconf,
- separate the two techniques (m4_errprintn and diversions) into separate
examples,
- Tweak the output so that it fits in 79 columns (in 'info' output).
2009-07-25 Bruno Haible <bruno@xxxxxxxxx>
Clarify autom4te debugging tips.
* doc/autoconf.texi (Debugging via autom4te): Clarify that the two
techniques are independent.
*** doc/autoconf.texi.orig 2009-07-25 16:39:05.000000000 +0200
--- doc/autoconf.texi 2009-07-25 16:36:28.000000000 +0200
***************
*** 12454,12463 ****
version is 2.63b.95-3963
@end example
! Another trick is using @code{m4_errprintn} to output debugging messages
! to standard error with no further m4 expansion, and without interfering
! with the post-processing done to standard output. For example, contrast
! these two attempts to learn how @code{m4_dquote} is implemented:
@smallexample
$ @kbd{cat <<\EOF > foo.m4}
--- 12454,12485 ----
version is 2.63b.95-3963
@end example
! Another trick is to print out the expansion of various m4 expressions
! to standard error or to a file, with no further m4 expansion, and without
! interfering with the post-processing done to standard output. There are
! two ways to do this. One is through @code{m4_errprintn}, the other one
! through diversions in @command{autom4te}.
!
! @code{m4_errprintn} shows a given expression on standard error. For
! example, if you want to see the expansion of an autoconf primitive or
! of one of your autoconf macros, you can do it like this:
!
! @smallexample
! $ @kbd{cat <<\EOF > configure.ac}
! AC_INIT
! m4_errprintn([Here comes the definition of AC_DEFINE_UNQUOTED:])
! m4_errprintn(m4_defn([AC_DEFINE_UNQUOTED]))
! AC_OUTPUT
! EOF
! $ @kbd{autoconf}
! Here comes the definition of AC_DEFINE_UNQUOTED:
! _AC_DEFINE_Q([], $@@)
! @end smallexample
!
! You can also use diversions. For example, the following is an attempt
! to learn how @code{m4_dquote} is implemented. Note that diversion 0
! is standard output, and standard output is being redirected to a file
! through the @samp{-o output} option.
@smallexample
$ @kbd{cat <<\EOF > foo.m4}
***************
*** 12466,12491 ****
m4_divert([0])dnl
try two: [m4_dquote is ]m4_defn([m4_dquote])
m4_dquote([hi])
EOF
! $ @kbd{autom4te --language=m4sugar -o foo foo.m4}
foo.m4:2: error: possibly undefined macro: m4_dquote
! If this token and others are legitimate, please use m4_pattern_allow.
! See the Autoconf documentation.
! $ @kbd{cat foo}
! try two: m4_dquote is [$@@]
! [hi]
! $ @kbd{cat <<\EOF > foo.m4}
! m4_init
! m4_errprintn([try one: m4_dquote is ]m4_defn([m4_dquote]))
! m4_divert([0])dnl
! m4_errprintn([try two: m4_dquote is ]m4_defn([m4_dquote]))dnl
! m4_dquote([hi])
! EOF
! $ @kbd{autom4te --language=m4sugar foo.m4}
! try one: m4_dquote is [$@@]
try two: m4_dquote is [$@@]
- $ @kbd{cat foo}
[hi]
@end smallexample
@node Programming in M4sh
--- 12488,12503 ----
m4_divert([0])dnl
try two: [m4_dquote is ]m4_defn([m4_dquote])
m4_dquote([hi])
+ m4_dquote(tic, tac, toe)
EOF
! $ @kbd{autom4te --language=m4sugar -o output foo.m4}
foo.m4:2: error: possibly undefined macro: m4_dquote
! If this token and others are legitimate, please use m4_pattern_allow.
! See the Autoconf documentation.
! $ @kbd{cat output}
try two: m4_dquote is [$@@]
[hi]
+ [tic],[tac],[toe]
@end smallexample
@node Programming in M4sh
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